A South Korean teenager who went missing in Turkey near the Syrian border had images of what appeared to be Islamic State in Iraq and the Levant (ISIL) militants on his home computer, police said on Monday, amid suspicions he may have joined the group.

The 18-year-old, identified only by his surname Kim, went missing on January 10 during a trip to the southern Turkish town of Kilis and was last seen leaving a hotel.

Turkish newspaper Milliyet reported earlier that he had exchanged e-mails with the ISIL group and probably crossed into Syria to join them.

But Seoul's foreign ministry said at the weekend it had seen no hard evidence that Kim had entered Syria or joined the group.

South Korean police investigating his disappearance searched Kim's room in Seoul and checked his personal computer.

"There were some photos of gun-toting militants carrying what look like ISIL flags in his computer," a Seoul police detective on the case told AFP on the condition of anonymity.

Police are looking to see if Kim accessed any ISIL-linked websites and analyzing e-mail exchanges with a Turkish friend he met online known as "Hassan," the detective said.

Kim's parents allowed him to travel to Turkey, along with a family friend, after he pleaded for the chance to meet with Hassan in person.

At home, Kim spent most of his time playing computer games after dropping out of school a few years ago, Dong-A Ilbo and other major newspapers reported.